This invention relates to an oil well shear tool which may be used in a sucker rod string or in a fishing tool string.
In the typical producing oil well, a pump is secured to the lower end of a sucker rod string and is vertically oscillated by means of pumping equipment of the walking beam type. If the sucker rod string should fail or shear between the upper and lower ends thereof, it is necessary for the upper portion of the sucker rod string to be first removed from the well with fishing operations then being conducted to retrieve the lower portion of the sucker rod string and the pump at the lower end thereof. It has been found desirable to provide a shear tool near the lower end of the sucker rod string which will shear upon a predetermined amount of stress being experienced by the string. It has been found desirable to cause the shear near the pump since it is easier to fish the pump from the well than a long string of sucker rods.
Shear tools have been provide which include a shear portion designed to shear upon predetermined stress being subjected thereto. However, the fluid being pumped is normally very corrosive and the shear portion is subjected to corrosion which dramatically affects the shear characteristics. An attempt has been made in prior art shear tools to prevent the corrosion of the shear portion by encapsulating or coating the shear portion with plastic but the plastic material quickly chips or peels therefrom. A second disadvantage in the prior art shear tools is that the shear portions thereof tend to deflect thereby causing premature failure of the shear portion.
Therefore, it is a principal object of the invention to provide an improved shear tool for use in oil wells.
A further object of the invention is to provide an oil well sucker rod shear tool including means for preventing the shear portion thereof from being sujected to the corrosive fluid being pumped.
Still another object of the invention is to provide a shear tool including means for preventing deflection of the shear portion.
Still another object of the invention is to provide a shear tool which may be used with fishing tools or which may be used with sucker rods.
These and other objects will be apparent to those skilled in the art.